U.S. Pat. No. 3,550,925 illustrates an apparatus that can be used to separate metals of different melting points and includes an inclined retort which is mounted for rotation within a gas furnace. The material to be processed is charged in the upper end of the retort, and as the material is conveyed downwardly within the retort it is heated and the lower melting point metal will be melted and separated from the higher melting point metal.
With a structure as disclosed in the aforementioned patent, combustible waste gases are generated through the processing and discharged from the upper end of the retort. For pollution control, the gases are normally passed through a cyclone separator to remove the particulate material and then passed through an afterburner where the combustible gases are fully combusted.
The apparatus as disclosed in U.S. Pat. No. 3,550,925 can also be used to remove oil, or other combustible contaminants, from metal scrap, such as borings, turnings, chips, and the like. The oil will vaporize as the scrap is heated and a portion of the vaporized oil will be burned in the retort, while the remaining portion of the oil vapor, as well as the gases of combustion, will be conducted to an afterburner for final combustion. With this type of process, accurate temperature and atmospheric control must be maintained in order to volatilize and partially combust the oil, while not oxidizing, melting, or fusing the metal scrap.